Water purification by means of a reverse-osmosis filter membrane has become well recognized as producing water of excellent quality. However, many prior art water purifiers are not well adapted for home use. A common failing has been a requirement that water flow continually through the unit, even when its storage tank was full of purified water, causing an obvious waste of water. Some prior water purifiers require a pressurized container for receiving the pure water, resulting in variations in delivery pressure and undesirable back pressure on the reverse-osmosis filter membrane. Mechanical valve actuators have been incorporated in water purifier systems, and in other instances certain of the valves were electrically operated. These have added to manufacturing and installation costs, decreased reliability, and in some instances made the purifiers somewhat difficult to operate.
The system disclosed in my U.S. Pat. No. 4,176,063 represents an efficient water purifier for hoome and other uses, operated entirely hydraulically upon opening and closing of the faucet that dispenses the purified water. However, this system suffers from certain disadvantages. A major problem is that it requires a multiplicity of exterior hoses connecting various valve elements and controls. The result is a proliferation in the number of parts making up the purifier, adding to the complexity and expense of manufacture and servicing. A fitting is required at each hose connection, each one having a potential for leakage. The multipart purifier with its exterior hoses becomes unduly bulky, and its appearance suffers. Moreover, the construction and operation of certain control valves, such as the pilot valve and the shutoff valve to prevent dissipation of squeeze water as the pure water is being forced to the tap, can be improved upon for reliability and simplicity.
A major servicing problem with prior water purifiers has centered around the reverse-osmosis filter membrane, which must be removed and replaced periodically. This has involved removing the water purifier from underneath the sink and disconnecting various water lines. The filter membrane then must be removed from the pressure vessel by forcing a rod down through one end of the vessel to push the filter membrane out the other. This has required skilled service personnel, and is a time-consuming and expensive operation.
In a fully automatic and hydraulically operated water purifier, such as that of U.S. Pat. No. 4,176,063, it is necessary to include a check valve in the pure water line to trap water under pressure in the line that leads to the faucet. This is essential as the pressure of this water is used in effecting operation of other control valves in the system. This check valve must work with great rapidity and be fluid-tight when closed to prevent dissipation of the pressure after the faucet is closed. The volume of water involved is relatively small so it takes little reverse flow to cause a major reduction in the pressure of the water trapped by the check valve. A simple ball check valve has been found to be completely unsatisfactory. Other check valves, such as the fluid operated valve shown in the aforementioned patent, or a flapper-type check valve, do not operate with the speed necessary to prevent a significant drop in pressure after the faucet is closed. This presents the risk that there may be insufficient pressure available to operate certain of the control valves, especially in areas where water supply pressure is relatively low. Moreover, water flowing in the reverse direction past the check valve before full closing of this valve can create an unpleasant sound. Consequently, there has been a need for an improved check valve in water purifier systems.